Team 2 : Dynamics of the translation machinery nanomachines and metabolic cross-talks

Team leader: Hubert BECKER

Research topics

The team is a part of the UMR 7156 (partner 1). The team aims at identifying and studying the macromolecular edifices involved in the nucleus-mitochondria crosstalk that allows S. cerevisiae to respire. Among these, part of their effort will be concentrated on the particles to which components of the translation machinery participate. In the frame of this general goal, the team will develop the following sub-projects: i) to study in yeast and human cells the mechanisms of aminoacyl-tRNA Synthetases involvement in nucleus-mitochondria cross-talk; ii) to investigate the link between nuclear export and channeling of tRNA and the shift to the respiratory metabolism; iii) in the expectation that the use of cytosolic retention platforms is a widespread strategy to control the localizations and roles of multifunctional proteins during adaptation responses.

Role in MitoCross

The first task will be to study the dynamics of the AME complex and the nucleus-mitochondria crosstalk. We have so far shown that the nuclear pool of some aminoacyl-tRNA synthetases can act as a transcription factor for genes encoding some of the mitochondrial respiratory chain subunits. Our primary analysis was restricted to a small, but obvious, subset of genes necessary for the respiratory metabolism. We now want to identify the entire pool of genes that are under transcriptional control of cMRS and to study if AME nanoparticle has the capacity of a yeast cell to switch to the respiratory metabolism.

The second task will be to identify tRNA channelling factors and adaptation to respiration. The recent discovery that tRNA channelling is not unidirectional prompted us to verify whether tRNA trafficking might be connected to other cellular circuits and in particular to nutrient sensing. We will investigate this possibility by making an in depth structural and functional study of already identified tRNA channelling factors.

The third task will be to study human mitochondrial transamidation pathway. In Human cERS is fused, via a linker composed of three so-called WHEP repeats to prolyl-tRNA synthetase forming the bifunctional glutamylprolyl-tRNA synthetase (EPRS) which is sequestered in a large cytosolic multisynthetase complex called the MARS complex by binding to an auxiliary, non-synthetase, protein called p38. Our working hypothesis is that a variant of EPRS escapes sequestration by p38, binds to Hsp90 that serves as cargo prior its import into human mitochondria where it participate to the mitochondrial transamidation pathway. Our objective is to identify using various approaches the variants of the human EPRS which can be imported into human mitochondria. Once identified, we intend to decipher the pathway leading to mitochondrial import of this variant.

The forth task will be to identify other dual-localized proteins and their cytosolic retention anchors In the light of our recent findings concerning the role of Arc1p as a retention platform, we believe that the use of dual-localized proteins is a more generalized strategy used by cells to interconnect and coordinate different cellular and/or metabolic pathways. This fourth goal of the project is to set up a screening strategy based on the use of the Split-GFP tool, to identify proteins that have a secondary subcellular localization in response to various stimuli or stresses.